The long-term objectives of this proposed project are to develop a "Test Kit" for quantitative assessment of fat malabsorption in infants without the need for control of dietary fat intake and quantitative collections of stools for several days as is the case with the current "Gold Standard", viz. The 72-hour fecal fat method. Our proposed "Test Kit" is based on administering a feeding of milk (or formula) containing a suitably labeled 13C-triglyceride (13C-TG), a trace amount of the nonabsorbable marker dysprosium chloride (DyCl3) and the visual marker Brilliant Blue followed by laboratory analysis of Dy and 13C-Excess in a sample of stool containing the visual marker. All components of the proposed "Test Kit" have been validated except for the specific nature of the 13C-TG suitable for use with infants. Based on the known triglyceride composition and fatty acid positional specificity of lipids of infant's diet, we hypothesize that the 13C-TG 1,3-dioleoyl-2-(13C) palmitoyl glycerol is a suitable marker for this purpose. Thus, during Phase-I of the proposed project, we will conduct a limited protocol in infants with fat malabsorption to examine the quantitative relationship between fecal excretion of the proposed 13C- TG and 72-hour fecal fat. PROPOSED COMMERCIAL APPLICATION: The proposed Phase-I and Phase-II research will be sufficient reliable data that permit customized manufacture of a "Test Kit" specifically for accurate assessment of fat digestion/absorption in infants.